The 25-year-old Costa impressed for Atletico Madrid last season as they won the title in Spain and has now joined Chelsea after they met the £32m buy-out clause in his contract.

And Mourinho told Sky Sports: “He’s a great addition for us. He is a fantastic player.

“Technically he is very, very good. That’s why, lots of the players, they are so happy and so surprised, because his quality is even higher than what they expect.

“He is so strong physically and he gives so much effort during matches.

"He’s a great addition for us. He is a fantastic player. Technically he is very, very good. That’s why, lots of the players, they are so happy and so surprised, because his quality is even higher than what they expect."Jose Mourinho

“When somebody sees him play, the first thing that gets into their eyes is exactly that, the capacity to work hard for the team, and to be so powerful and so strong physically.

“To have Diego, (Fernando) Torres and (Didier) Drogba as our strike force is something that gives us different qualities. We are really strong in that position now.”

Chelsea great Drogba is back at the club after two seasons away and, although he is 36 now, Mourinho says the striker still has the attributes needed to be a success in the Premier League.